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Major flu strain resistant to leading drug

There’s some troubling health news being reported today: It turns out virtually all the flu in the United States this season are resistant to the leading anti-viral drug Tamiflu.

Scientists and health officials are ouzzled. Here’s an excerpt from a New York Times story:

The problem is not yet a public health crisis because this has been a below-average flu season so far, and because the Tamiflu-resistant strain, one of three circulating, is still susceptible to other drugs. But infectious disease specialists are worried nonetheless.

Last winter, about 11 percent of the throat swabs from patients with the most common type of flu that were sent to the Centers for Disease Control and Prevention for genetic typing showed a Tamiflu-resistant strain. This season, 99 percent do.

“It’s quite shocking,” said Dr. Kent A. Sepkowitz, director of infection control at Memorial Sloan-Kettering Cancer Center in New York. “We’ve never lost an anti-microbial this fast. It blew me away.”

The single mutation that creates Tamiflu resistance appears to be spontaneous, and not a reaction to overuse of the drug. It may have occurred in Asia, and it was widespread in Europe last year. In response, the disease control agency issued new guidelines two weeks ago. They urged doctors to test suspected flu cases as quickly as possible to see if they are influenza A or influenza B, and if they are A, whether they are H1 or H3 viruses.

The only Tamiflu-resistant strain is an H1N1. Its resistance mutation could fade out, an agency scientist said, or a different flu strain could overtake H1N1 in importance, but right now it causes almost all flu cases in the country, except in a few mountain states, where H3N2 is prevalent.